Method of making pure salt from FRAC-water/wastewater

ABSTRACT

The present invention relates to a method for making pure salt comprising recapturing post-drilling flowback water from hydro-fracturing; removing oil from the flowback water; filtering the flowback water using an ultra filter with a pore size of about 0.1 microns or less to remove solid particulates and large organic molecules, such as benzene, ethylbenzene, toluene, and xylene, from the water; concentrating the flowback water to produce a brine that contains from about 15 wt % to about 40 wt % of salt relative to the total weight of the flowback brine; performing one or more chemical precipitation processes using an effective amount of reagents to precipitate out the desired high quality commercial products, such as, barium sulfate, strontium carbonate, calcium carbonate; and crystallizing the chemically treated and concentrated flowback brine to produce greater than 99.5% pure salt products, such as sodium and calcium chloride.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/220,389 filed Jun. 25, 2009, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Many mining and natural gas exploration/production activities generatewater contaminated with significant concentrations of chemicals andimpurities, eventually being discharged into surface water as well assub-surface aquifers.

This seriously negatively impacts the quality of water used fordrinking, as well as for other domestic and commercial needs. In manyareas, the wastewater from drilling and mining operations have renderedregional water supplies unusable.

Hydro-fracturing is one of those mining and natural gas explorationproduction activities that generates waste water. The well-drillingprocess is involves injecting water, along with sand and a mixture ofchemicals (known as fracking fluid) under high pressure into abedrock/shale formation via the well. The method is informally calledfracking or sometimes hydro-fracking, and is intended to increase thesize and extent of existing bedrock fractures. The process involvespumping water into fractures at pressures exceeding 3000 psi and flowrates exceeding 85 gallons per minute in order to create long fracturesand pack intersecting with natural fractures in the shale therebycreating a flow channel network to the wellbore. The fracture width istypically maintained after the injection by sand, ceramic, or otherparticulates that prevent the fractures from closing when the injectionis stopped. Hydro-fracturing releases the methane gas trapped in thenatural fractures or pores of the shale so it can flow up the pipe

The hydro-fracturing process can use a huge volume of water—up to aboutseveral million gallons of water per well. A horizontal well with a4,500 foot lateral bore, for example, uses about 4 to 5 million gallonsof water per well. Accordingly, the hydro-fracturing process can drawmillions of gallons of freshwater for use as source water, depletingclean water sources and disturbing the habitat of wildlife.

Hydro-fracturing also generates huge quantities of wastewater.Hydro-fracturing fluids which are injected into a well may containchemicals that can be toxic to humans and wildlife, including chemicalsthat are known to cause cancer. These include substances such as: dieselfuel, which contains benzene, ethylbenzene, toluene, and xylene. Some ofthese chemicals, such as benzene, are considered carcinogenic at verylow concentrations.

The flowback water, which is the fluid that comes back up afterhydro-fracturing, can include the chemicals pumped in plus bothnon-toxic and toxic substances that may be present in the shaleformation.

Because of the potential negative impact to the environment caused byusing hydro-fracturing processes, regulatory agencies are considering aban on the further issuance of permits.

Accordingly, there is a need for greener technology in drilling wellsusing hydro-fracturing process including, resulting in purified watercontaining which can be safely returned to environment. There is also aneed to generate over 99% pure salt from the wastewater of thehydro-fracturing process, which can be used commercially, therebylowering the overall cost of the greener technology in drilling wells asdescribed herein, making its use more desirable.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention relates to methods for making puresalt from wastewater, and more particularly, methods of making pure saltfrom wastewater generated using hydro-fracturing process.

In another aspect of the present invention relates to methods forgenerating pure salt, along with purified water, which contains lessthan 500 ppm, preferably less than 300 ppm, and more preferably lessthan 100 ppm of Total Dissolved Solids (TDS). In terms of solids, thisprocess can, in some embodiments, generate water, which is cleaner thanthe tap or bottled water.

In yet another aspect of the present invention relates to methods formaking other high quality commercial products, such as barium sulfate,strontium carbonate, calcium carbonate, sodium hypochlorite and lithiumhypochlorite.

In accordance with an embodiment of the present invention, a method formaking pure salt comprises recapturing post-drilling flowback water fromhydro-fracturing; removing oil from the flowback water (preseparation);filtering the flowback water using an ultra filter with a pore size ofabout 0.1 microns or less to remove solid particulates and large organicmolecules, such as benzene, ethylbenzene, toluene, and xylene, from thewater (ultrafiltration); concentrating the flowback water to produce abrine that contains from about 15 wt % to about 40 wt %, preferably fromabout 20 wt % to about 35 wt %, and more preferably from about 25 wt %to about 30 wt % of salt relative to the total weight of the flowbackbrine (brine concentration); performing one or more chemicalprecipitation process using an effective amount of reagents toprecipitate out the desired high quality commercial products, such as,barium sulfate, strontium carbonate, calcium carbonate (chemicalprecipitation); and crystallizing the chemically treated andconcentrated flowback brine to produce greater than about 98%,preferably about 99% or more, more preferably about 99.5% or more, andmost preferably about 99.7% or more of a pure salt, such as sodium andcalcium chloride (crystallization).

In one embodiment, the source water for hydro-fracturing process isobtained from one or more sources including, but not limited to,pretreated orphaned/abandoned mine drainage water, pretreated otherwastewater, freshwater, and recycled condensates from one or moreevaporator units in the concentration and/or crystallizing steps.

In accordance with an aspect of the invention, before the chemicalprecipitation, the chemical constituents and amounts of those chemicalconstituents in the concentrated flowback brine are identified and/orquantified to determine an effective amount of reagents to be usedduring chemical precipitation. This can maximize the yield of certainhigh quality commercial products, for example, barium sulfate, strontiumcarbonate, calcium carbonate and the salt products. In one embodiment,the chemical precipitation process is performed after the brineconcentration step. In another embodiment, the chemical precipitationprocess is performed before the brine concentration step. In yet anotherembodiment, the chemical precipitation process is performed at twostages, i.e., first, either before or after the brine concentrationstep, and second, after the crystallization step.

In accordance with yet another aspect of the invention, the steps ofremoving oil from the flowback water, filtering the flowback water, andconcentrating the flowback water to form a brine are performed “on-site”which means at the site of drilling (does not require transport); andthe steps of performing chemical precipitation process to removecontaminants from the concentrated flowback water, and crystallizing thechemically treated and concentrated flowback brine are performed at“off-site” which means a location which is remote from the drilling site(requires transport—not just pumping through conduits or pipes). Byperforming the step of concentrating hydro-fracturing brine on-site, theamount of brine to be transported to an off-site brine treatmentfacility is significantly reduced, thereby reducing the amount ofpollution created by trucks transporting brine. This also minimizes thedamage done to roads and reduces overall cost related to trucking. Inaddition, the water produced during the step of concentrating flowbackwater using an evaporator to create a brine using one or moreevaporators, reverse-osmosis or both or any other technique, such asdistillation, may be reused as the source water for hydro-fracturingprocess, reducing the amount of water needed from other sources.

In another embodiment, all of the steps, i.e., steps of removing oil,filtering, concentrating the amount of salt in the brine, performingchemical precipitation, and crystallizing the chemically treated andconcentrated flowback brine to produce over 98% pure salt are performedat an “off-site” facility.

When the flowback water is transported directly to an “off-site”treatment facility, chemical precipitation can be performed before orafter the flowback water is concentrated.

When the flowback water is first treated on-site, for example, at amobile treatment plant, then the flowback water is first concentrated tocreate a brine, followed by a chemical precipitation process.

In a preferred embodiment, the step of concentrating the flowback waterto produce a brine is done by using one or more evaporator, such as amechanical vapor recompression or forced circulation type evaporator, byone or more reverse osmosis or some combinations thereof.

In one aspect of the invention, the pure salt products produced by thestep of crystallizing the concentrated brine is selected from the groupconsisting of a dry salt of sodium chloride, a salt solution of calciumchloride, and mixtures thereof. In one embodiment of the invention, thesalt solution of calcium chloride is further processed to producecalcium chloride in the form of dry salt. In another embodiment of theinvention, the sodium chloride is further processed to produce sodiumhypochlorite.

In an aspect of the invention, certain high quality commercial products,such as barium sulfate, strontium carbonate, and calcium carbonate, canbe recovered from the flowback brine to be sold as commodities. In oneembodiment of the present invention, barium sulfate is obtained byperforming the chemical precipitation process after the brineconcentration step. In yet another aspect of the invention, anadditional chemical precipitation process is performed after thecrystallization step to precipitate out strontium carbonate, calciumcarbonate, and mixtures thereof.

The present invention is a significant advance. Rather than merelydiluting the post-drilling flowback water through a municipal wastewatertreatment facility before it is discharged to the environment, thepresent invention allows large quantities of concentrated brinesolutions of poor quality containing various contaminants into over 99%,pure commercial grade dry salt, and over 99% pure commercial gradeconcentrated salt solution and allows for reuse of significantquantities of water. In addition to the high quality commercial productsand pure salts produced, the present invention concurrently producespurified water which, in some embodiments, contains less than 500 ppm,preferably less than 300 ppm, and more preferably less than 100 ppm ofTotal Dissolved Solids (TDS). Moreover, the present invention also makesor facilitates production of other high quality commercial products,such as barium sulfate, strontium carbonate, calcium carbonate, sodiumhypochlorite and lithium hypochlorite.

The present invention not only provides environmentally friendlysolutions to hydro-fracturing well drilling process, but also provides acost effective solution by producing these high quality commodities,e.g., pure salts, such as sodium chloride and calcium chloride, sodiumhypochlorite, barium sulfate, strontium carbonate, calcium carbonate,and lithium hypochlorite.

The present invention also provides more environmentally friendly andcost effective process by providing mobile treatment plant, allowing thecondensate which is purified water containing less than 500 ppm TDS tobe reused as source water for the well drilling/hydro-fracturingprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a generalized process flow diagram illustrating oneembodiment of the present invention.

FIG. 2 is a generalized process flow diagram illustrating anotherembodiment of the present invention.

FIG. 3 is a flow diagram illustrating the stage 1 reverse osmosis aspectin accordance with an aspect of the invention.

FIG. 4 is a flow diagram illustrating the chemical treatment step inaccordance with an aspect of the invention.

FIG. 5 is a flow diagram illustrating the chemical treatment step inaccordance with another aspect of the invention.

FIG. 6 is a flow diagram illustrating the crystallization step inaccordance with an aspect of the invention.

FIG. 7 is a generalized process flow diagram including thecrystallization step using a mechanical vapor recompression evaporator.

DETAILED DESCRIPTION

While the specification concludes with the claims particularly pointingand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description. Allpercentages and ratios used herein are by weight of the totalcomposition and all measurements made are at 25° C. and normal pressureunless otherwise designated. All temperatures are in Degrees Celsiusunless specified otherwise.

The present invention can comprise (open ended) or consist essentiallyof the components of the present invention as well as other ingredientsor elements described herein. As used herein, “comprising” means theelements recited, or their equivalent in structure or function, plus anyother element or elements which are not recited. The terms “having” and“including” are also to be construed as open ended unless the contextsuggests otherwise. As used herein, “consisting essentially of” meansthat the invention may include ingredients in addition to those recitedin the claim, but only if the additional ingredients do not materiallyalter the basic and novel characteristics of the claimed invention.Preferably, such additives will not be present at all or only in traceamounts. However, it may be possible to include up to about 10% byweight of materials that could materially alter the basic and novelcharacteristics of the invention as long as the utility of the compounds(as opposed to the degree of utility) is maintained.

All ranges recited herein include the endpoints, including those thatrecite a range “between” two values. Terms such as “about,” “generally,”“substantially,” and the like are to be construed as modifying a term orvalue such that it is not an absolute, but does not read on the priorart. Such terms will be defined by the circumstances and the terms thatthey modify as those terms are understood by those of skill in the art.This includes, at very least, the degree of expected experimental error,technique error and instrument error for a given technique used tomeasure a value.

The term “effective amount” as used herein, refers to a sufficientamount of reagents to precipitate out the various chemical constituentsin the flowback water, which would then be able to produce pure saltand/or as appropriate, other high quality commercial products, such asbarium sulfate, strontium carbonate, calcium carbonate, sodiumhypochlorite.

Unless otherwise indicated, any and all numbers expressing quantities,chemical properties, concentrations, temperatures, weight and other suchnumerical data are to be understood as being prefaced in all cases bythe term “about”, unless otherwise specifically noted. In addition, thesteps of methods disclosed and claimed herein do not impose a specificorder on the performance of these steps, unless otherwise a particularorder is expressly indicated in the specification.

When referring to concentrations of contaminants or components in water,treated or untreated, or to properties of water such as pH or viscosity,unless otherwise indicated, those concentrations or numerical valuesshall refer to the results of the analytical testing of a typical sampletaken and analyzed by accepted laboratory methods and procedurescurrently used in the industry.

The present invention provides greener technology in drilling wellsusing hydro-fracturing process, which also produces producing highquality commercial products, e.g., over 99% pure salts, such as sodiumchloride and calcium chloride, and other high quality commercialproducts, such as sodium hypochlorite, barium sulfate, strontiumcarbonate, calcium carbonate and lithium, thereby lowering the overallcost of the greener technology.

In a preferred embodiment, and as illustrated in FIG. 1, the method ofthe present invention first recaptures post-drilling flowback water fromhydro-fracturing. Then, the flowback water goes through a preseparationstep to remove oil and grease (“O&G”) from the flowback water.Subsequently, the effluent from the preseparation step is introduced tothe ultrafiltration step. In this step, solid particulates and largeorganic molecules such as benzene, ethylbenzene, toluene, xylene andother contaimants, such as, for example microorganisms, are removed fromthe flowback water. We note that although the step is called“ultrafiltration” step throughout the application, the term“ultrafiltration” is not limited to filtering using an ultra filter, butalso encompasses any method of removing solid particulates and largeorganic molecules such as benzene, ethylbenzene, toluene, xylene andother contaimants, such as, for example microorganisms from the flowbackwater. Such method of removing solid particulates, organic moleculesand/or microorganisms may be done by using, for example, an ultrafilter, a micro filter, clarifier, carbon filter, an organic stripperand the like and any combinations thereof.

Next, the effluent from the ultrafiltration step is introduced to abrine concentration step, concentrating the amount of salt in theflowback water using an evaporator, reverse osmosis or both so that aconcentrated flowback brine is created. The brine comprises from about15 wt % to about 40 wt %, preferably from about 20 wt % to about 35 wt%, and more preferably from about 25 wt % to about 30 wt % of salt,preferably sodium chloride, relative to the total weight of theconcentrated flowback brine.

Then, the effluent from the brine concentration step goes through achemical precipitation process using an effective amount of reagents toremove desired high quality commercial products, including, but notlimited to barium sulfate, strontium carbonate, and/or calciumcarbonate, from the concentrated flowback brine. The effluent from thechemical precipitation process then proceeds to a crystallizationprocess to produce greater than about 98%, preferably about 99% or more,more preferably about 99.5% or more, and most preferably about 99.7% ormore pure dry and liquid salt products. The purified water containingless than 500 ppm TDS produced from the steps of concentrating andcrystallizing the brine can be returned to the environment or reused assource water for well drilling/hydro-fracturing process. The dry saltproduced from the crystallization step can be further process to makesodium hypochlorite.

The method comprising all of the steps above may be performed at anoff-site brine treatment facility. In a preferred embodiment, one ofmore of the steps of removing oil from the flowback water, filtering theflowback water, and concentrating the amount of salt in the flowbackwater to produce a brine are performed on-site; and the steps ofperforming chemical precipitation process using the effective amount ofreagents to remove contaminants from the brine, and crystallizing thechemically treated and concentrated flowback brine to produce over 98%pure salt are performed at off-site.

In still another embodiment, some concentration of the brine can beundertaken on-site and additional concentration can be undertakenoff-site.

The chemical precipitation process following crystallizing can generatethe desire high quality commercial products from the liquid saltproduct, such as strontium carbonate and calcium carbonate. In yetanother preferred embodiment, the method further comprises producingsodium hypochlorite from the dry salt product.

FIG. 1 illustrates one embodiment of the invention where the chemicalprecipitation process is performed after the brine concentration step.However, in another embodiment, the chemical precipitation process maybe performed before the brine concentration step. In yet anotherembodiment, the chemical precipitation process may be performed at twostages, i.e., first, either before or after the brine concentrationstep, and second, after the crystallization step.

According to another embodiment illustrated in FIG. 7, the recapturedflowback hydro-fraturing water 805 which may or may not have beenconcentrated on-site, is transported to an off-site facility where theflowback water is concentrated using an evaporator 810 to produce abrine containing from about 25 weight % of sodium chloride salt relativetotal weight of the concentrated brine, which is then exposed tochemical precipitation process 815 to obtain one or more high qualitycommercial products, such as barium sulfate, strontium carbonate, and/orcalcium carbonate. The effluent from the chemical precipitation step issubsequently crystallized using an mechanical vapor recompressionevaporator (MVR) 801 to produce over about 98%, preferably over 99%,more preferably over 99.5% pure salt products.

FIG. 2 illustrates yet another embodiment of a system for treatingcontaminated water and to produce pure salts. Source water 201 for theprocess may be from one or more sources, depending primarily ongeographical proximity of the well-drilling site to various types ofsource water. The source water includes, but not limited to anorphaned/abandoned mine drainage (“AMD”), wastewater (“WW”), freshwater,condensates from the on-site evaporator and/or concentration units, orcondensates from off-site evaporator and/or condensation units and/orwater resulting from later steps such as from crystallization units.

In case the source water is either AMD or WW 201, such water could betreated at the source or at a pretreatment facility 202 and then pipedor transported 102 to the drilling site. At the site, water may bedischarged into either holding tanks or temporary storage ponds beforehydro-fracturing.

The pretreatment process 202 can vary as to the quality/quantity ofsource water 201. Each batch of source water 201 could be pretreated tothe established regulatory parameters before introducing the pretreatedsource water 202 into the earth's substrata via the drilling process.

Pretreated source water 102 may flow into the drilling operation 203wherein it may be mixed with a number of chemicals/additives to alterthe suitability of the pretreated source water 102 to a particular phaseor requirement of the drilling and hydro-fracturing process. Theadditives may include materials known as fracturing gels, as well asviscosity reducers, friction reducers, clay and shale stabilizers, and anumber other additives. The flowback water (also may be referred hereinas fracwater) 103 which flows back out of the well 203 will be treatedin subsequent processes to remove these and other materials.

In one embodiment of the present invention, the untreated frac-water 103may flow into the treatment system on-site near the well 203. Thistreatment system may be mobile.

The daily volume of water 201 either used for drilling and/orhydro-fracturing and the daily volume of fracwater 103 flowing back outof the well on any given day can vary significantly. Based on the totaltime and total volume of water expected to be used under actualconditions, and the anticipated rate of the flowback of fracwater fromthe well, a working estimate used for illustration purpose only in theTables below is about 150,000 gallons per day. The actual volume ofwater may vary and may be greater or lower than the estimate.

Given that initial flowback conditions diminish rapidly with time,frac-tanks or holding ponds could be used to hold the untreatedfracwater collected from the well flowback. The storage volume could besized accordingly to contain the maximum daily flow of frac-water, fromwhich a certain amount of water would be drawn into the treatmentprocess and to produce pure salt.

The average daily rate of about 150,000 gpd may flow into an on-sitetreatment system. This on-site treatment system maybe mobile.

Preseparation

Preseparation may include an inclined plate separator to separate oiland/or grease and water, and also to remove large particulates from theflowback frac-water 103. Units manufactured by JDI, Inc., Hydroquip orother equivalents could be chosen and utilized for this purpose.Collected oil and/or grease 105 removed from the oil/water preseparationprocess using additional stages such as settling, aeration and/orskimming can be accumulated in a temporary storage tank and removed to apermitted receiving facility. Table 1 below indicates an example of theinfluent flow and targeted parameters for treatment and removal at thisfirst phase of post-drilling preseparation.

TABLE 1 Preseparation of Flowback Fracwater Influent Flow 150,015 gpdTDS (Total Dissolved Solids) 45,000 ppm TSS (Total Suspended Solids) 150ppm O&G (Oil and Grease) 100 ppm Effluent Flow 149,940 gpd TDS 45,000ppm TSS 15 ppm O&G 10 ppm Oil Water Rated Flow 175 gpm Separator- MediaPack 0.5 ft3/gpm Colescer Plate Spacing 0.75 in Solids Rated Flow 175gpm Clarification Plate Spacing 1.0 in O&G 0 Chemical None Dosing

Ultrafiltration

Following preseparation 204, the water 104 is subjected toultrafiltration 207. Ultrafiltration 207 uses a mechanical filter with apore size of from about 0.01 to about 0.1 micron. This filter willscreen out suspended solid particles, colloidal solids, and largeorganic molecules such as acrylamide, benzene, ethylbenzene, toluene,and xylene, and possibly even microorganisms in the flowback water 104.

Table 2 below indicates an example of influent and effluentcharacteristics for the ultrafiltration process 207 as well and thecomponents of the system.

TABLE 2 Ultrafiltration step Influent Flow 149,940 gpd TDS 45,000 ppmTSS 15 ppm O&G 10 ppm Effluent Flow 149,933 gpd TDS 45,000 ppm TSS 0 O&G0 Process Feed Capacity 21,000 gallons Tank-Frac Tank UltrafilterMembranes Tubular 8 mm .D PVDF Circ Pump 100 HP System SizeContainerized Chemical Reagents Sulfuric Acid Feed Pump-pH Caustic SodaAdjustment

As mentioned above, this step is not limited to filtering using an ultrafilter, but encompasses any method of removing solid particulates andlarge organic molecules such as benzene, ethylbenzene, toluene, xyleneand other contaimants, such as, for example microorganisms from theflowback water. Such method of removing solid particulates, organicmolecules and/or microorganisms may be done by using, for example, anultra filter, a micro filter, clarifier, carbon filter, an organicstripper and the like and any combinations thereof.

Both the preseparation 204 and ultrafiltration 207 stages are theprimary point of oil and/or grease separation and solids removal,removing an estimated 125 lb/day of oil and 170 lb/day of solids,primarily in the form of fracture rock and rock dust per 150,000 gallonsof fracwater 103.

Solids 106, 107 from preseparation and ultra-filtration 207 flow into asolids dewatering process 206. Influent and effluent rates of thatprocess as well as the system components are indicated on Table 3 below.Dewatered solids 108 from the process as well as the system componentsare indicated on Table 3. These dewatered solids may be sent to a properwaste disposal felicity.

TABLE 3 Solids Dewatering Influent Flow 900 gpd TSS 25,000 ppm Effluent-Flow 833 gpd Filtrate TSS 15 ppm Effluent- Mass 750 lb/d Solids %Moisture 75% Sludge Tank Capacity 5,000 gallon Type Cone Bottom ChemicalCoagulant/Floe Polymer Conditioning Filter Press Capacity 10 ft³ TypePlate & Frame

Liquid extracted from the solids dewatering step 206 in this process 109are returned to the preseparation process 204. Process water 109 couldalso be returned to source water holding facilities, pretreatmentfacilities 202, or could be further treated and released into thegeneral water supply.

Concentration/Brine Formation

Effluent water from ultrafiltration stage 207 next flows into a system300 which would concentrate the amount of salt in the flowback fracwater to reduce the volume of created brine.

There are various ways to concentrate the salt brine. For example, oneor more evaporator or one or more reverse osmosis devices or both, orany other suitable techniques such as distillation.

In an embodiment of the present invention, effluent water 110 fromultrafiltration stage 207 flows into the multistage reverse osmosisprocess 208, 209, 210, and then to one or more evaporators 211. In apreferred embodiment, the multistage reverse osmosis process step isoptional. The clean water distillate 301, 302 and 303 created in thisstep may be returned as source water for well-drilling/hydro-fracturingprocess or discharged to the environment. “Clean water distillate” referto water that is sufficiently clean to return to the environment,although it could be recycled and reused as source water forhydro-fracturing. Clean water distillate generally results from anevaporation step (with or without the use of R.O.), but can result fromuse of R.O. alone 303. If no R.O. step is used, the ultrafiltered water110 can flow directly into one or more evaporators 211. Evaporators 211include, without limitations, static ponds, distillation apparatus,condensers and the like. The clean water distillate created in this stepmay have less than 500 ppm of total dissolved solids, which is less thanthe amount of total dissolved solids from a tap water. In otherembodiments, the amount of total dissolved solids may be less than 300ppm or more preferably less than 100 ppm.

This step concentrates the amount of salt in the flowback water so thatthe concentrated flowback water becomes a brine (concentrated flowbackbrine) that contains from about 15 wt % to about 40 wt %, preferablyfrom about 20 wt % to about 35 wt %, and more preferably from about 25%wt % to about 30 wt % of salt relative to the total weight of theconcentrated flowback brine.

As noted earlier, use of reverse osmosis (“RO”) is an optional step usedin conjunction an evaporator 211 or other device used to concentrate theamount of salt in the flowback fracwater such as 115 or 116. FIG. 3describe the first stage of RO process 208. RO preferably operates atpressures between 200 and 2000 psi. Table 4 below exmplifies theinfluent and effluent characteristics and quantities, and the componentsof the process 208.

TABLE 4 Influent Flow 149,933 gpd TDS 45,000 ppm TSS 0 ppm O&G 0 ppmEffluent-Permeate Flow 82,810 gpd TDS 2,010 ppm TSS 0 O&G 0Effluent-Reject Flow 67,123 gpd TDS 101,000 ppm TSS 0 O&G 0 FeedTank-Frac Capacity 21,000 gallons Tank Reverse Osmosis Membrane Type TFCMembrane Spiral Wound Configuration Operating 1200 psi Pressure Pump HP120 HP

As illustrated in FIG. 2, from the first-stage RO process 208, theeffluent 111 (“permeate”) still has a reasonable high concentration oftotal dissolved solids (TDS) and is not ready to be discharged back intothe environment. It is, in short, not sufficiently clean to beconsidered clean water distillate. However, it may be returned directlyto the drilling operation 203 for reuse since it has been stripped oftotal suspended solids (TSS), oils and grease and large organicmolecules in addition to the greater than 0.01 micron sized materials inthe ultra-filtration 207 process. Reject effluent 112 flows to asecond-stage RO process 209 wherein the permeate 113 produced is againacceptable for reuse in the drilling process 203. Effluent 115 caninstead flow directly to one or more evaporators 211. Removal of thepermeate concentrates the dissolved solids in the reject effluent 116 or117. Table 5 indicates the influent and effluent characteristics andlists the components of the second stage RO process 209. At this pointin the fracwater/wastewater reclamation and purification process, about67,000 gallons of the 150,000 gallon daily input of fracwater 103 remainas reject effluent 119 after being discharged 115, 116 from the firstand second stage RO processes. The other 83,000 gallons of permeate 111,113 from both processes 208, 209 can be returned 114A directly to thedrilling process 203.

TABLE 5 Influent Flow 67,123 gpd TDS 101,000 ppm TSS 0 ppm O&G 0 ppmEffluent-Permeate Flow 10,963 gpd TDS 3,670 ppm TSS 0 O&G 0Effluent-Reject Flow 56,160 gpd TDS 120,000 ppm TSS 0 O&G 0 FeedTank-Frac Tank Capacity 21,000 gallons Reverse Osmosis Membrane Type TFCMembrane Disc Stack Configuration Operating 1750 psi Pressure Pump HP 75HP

Effluent from the second stage RO process 209 flows to an RO polisher210 to produce extremely high quality permeate 118 which can qualify asa clean water distillate that can be returned to streams or water bodiesin the environment 124. This water can also sent back to the welldrilling site and the water 303 can be reused as hydro-fracturing water.Table 6 indicates the anticipated volumes and characteristics of thesecond stage RO influent and effluent.

Reject effluent 119 from the first and/or second stage RO processes 208,209 flows into an evaporation unit 211 at the drilling site. The purposeof this step is to further concentrate the flowback water from the ROprocesses 208, 209 before introducing the effluent to both chemicaltreatment and crystallization processes. As noted earlier, since RO isoptional, effluent 110 could flow directly into an evaporator 211 as areject effluent 119.

The evaporator 211 may be any device including a flash point evaporatoror flush point evaporator. Flash point evaporation is accomplished byfirst heating the flowback water, then pumping into a low-pressure tank.Because the boiling point of water drops with the decrease inair-pressure, the water will then vaporize almost immediately, flashinginto steam. The steam is then condensed into clean water. The wasteproduct 120 of this process is a solution with a high saltconcentration, which also contains small organic materials, inorganicmaterials including, but not limited to high quality commercialproducts, such as barium sulfate, strontium carbonate, and calciumcarbonate and/or other contaminants. This concentrated flowback brinefrom the evaporator may fed into the chemical treatment process 212 toprecipitate out small organic materials, inorganic materials including,but not limited to high quality commercial products, such as bariumsulfate, strontium carbonate, and ancalcaium carbonate and/or othercontaminants from the concentrated flowback brine before producinggreater than about 98%, preferably about 99% or more, more preferablyabout 99.5% or more, and most preferably about 99.7% or more pure saltin the crystallization step. The clean distillate water recovered can besent back to the well drilling site to be used as hydro-fracturing water302 and 303, or returned to the environment 118 and 301.

An evaporator 211, may also be a mechanical vapor recompressionevaporator, which generally contains a multi-effect evaporator train,which operates at successively lower pressure and temperatures. Steamfrom a high-pressure evaporator boils water into an adjacent lowerpressure evaporator.

Vapor compression involves pulling vapors from the low pressureevaporator, compressing the resulting vapor, and then returning them tothe high-pressure evaporator to use the pressurized vapor as a heatsource to evaporate additional feed water. The waste product from theseprocesses is a solution 120 with a high salt concentration with otherconstituents therein. Multiple evaporation stages using the same ordifferent devices may also be used. Moreover, the concentration step maybe accomplished on-site, off-site or both.

This concentrated flowback brine from the mechanical vapor recompressionsystem or other evaporator 120 may fed into the chemical treatmentprocess 212 to precipitate out small organic materials, inorganicmaterials including, but not limited to high quality commercialproducts, such as barium sulfate, strontium carbonate, and calciumcarbonate and/or other contaminants from the concentrated flowback brinebefore producing greater than about 98%, preferably about 99% or more,more preferably about 99.5% or more, and most preferably about 99.7% ormore pure salt in the crystallization step. The water removed from theprocess, such as that which evaporates, is clean enough to be returnedto the environment 301 or used as source water 302.

Chemical Precipitation Process

As shown in FIG. 2, the concentrated brine 120 may be exposed to one ormore chemical precipitation processes 212A to recover high qualitycommercial products, such as barium sulfates, strontium carbonates andcalcium carbonates, which can be sold as commodities, and/or to producesalt products (dry and liquid). Thereafter, the chemically treated brinemay be subjected to one or more crystallization steps 212B.

Additional chemical precipitation process may be performed after thecrystallization step(s) 212B to precipitate out the additional highquality commercial products.

When the flowback water is transported directly to an off-site treatmentfacility, chemical precipitation process 212A may be performed before orafter the water is concentrated. However, if the flowback water may befirst treated on-site at the drilling site using the mobile treatmentplant as illustrated in FIG. 1, then the flowback water may be firstconcentrated on-site, and subsequently, the concentrated brine may betransported to the off-site treatment facility to undergo chemicalprecipitation and crystallization steps. In another embodiment of theinvention, the flowback water may also be chemically treated on-site.

As shown in FIG. 4, in an embodiment of the present invention, bariumsulfate (BaSO₄) 405 and strontium carbonate (SrCO₃) and calciumcarbonate (CaCO₃) 530 may be obtained during the chemical precipitationstep before the effluent is concentrated 440 and subsequently sent tothe crystallization step 445 to obtain salt products 550 and 551.Various reagents that can be used in one or more chemical precipitationsinclude, but are not limited to, sodium sulphate, potassiumpermanganate, aluminum chloride, sodium carbonate, sodium hydroxide,hydrochloric acid, and mixtures thereof.

In one embodiment, the concentrated brine chemical treatment processemploys a two-stage chemical precipitation process. In the first stage,reagents, including but not limited to, hydrochloric acid (HCl) 403,sodium sulphate (NaSO₄) 401, and/or potassium permanganate (KMNO₄) 402,may be added in mixing tank #1 510 containing the flowback water orbrine (depending on whether the flowback water has been previouslyconcentrated or not). The flowback water or brine is chemically treatedin the mixing tank #1 510 and the pH may be adjusted to from about 3.5to about 4.0. The pH may be further adjusted in mixing tank #2 515 byintroducing sodium hydroxide (NaOH) 404 prior to separation of bariumsulfate 405. A flocculation aid (such as polymer and hydrochloric acid)from the polymer coagulant tank 525 may also be added to the mixing tank#2 515 prior to separation of barium sulfate 405.

In the second stage, reagents, including but not limited to, sodiumhydroxide (NaOH) 404, sodium carbonate (Na₂CO₃) 517, a flocculation aidfrom the polymer coagulant tank 525 may be added to mixing tank #3 520,along with the effluent from mixing tank #2 515. The flowback water orbrine is then chemically treated in the mixing tank #3 520 and the pHmay be adjusted to from about 11.5 to about 12.0 prior to separation ofstrontium carbonate and calcium carbonate 530. The effluent from thesecond precipitation step may be subsequently sent to a concentrationstep 440 and a crystallization step 445 to obtain dry salt 550 which maybe further processed to make sodium hypochlorite 552 or liquid saltsolution 551.

FIG. 5 shows another embodiment of the chemical precipitation process ofthe present invention, where barium sulfate (BaSO₄) 605 is precipitatedout before collection of salt products 650, 651, and strontium carbonate(SrCO₃) and/or calcium carbonate (CaCO₃) are separated out from thecollected salt solution 651.

In the first stage, reagents, including but not limited to, hydrochloricacid (HCl) 603, sodium sulphate (NaSO₄) 601, and/or potassiumpermanganate (KMNO₄) 602, may be added in mixing tank #1 610 containingthe flowback water or brine (depending on whether the flowback water hasbeen previously concentrated or not). The flowback water or brine ischemically treated in the mixing tank #1 610 and the pH may be adjustedto from about 3.5 to about 4.0. The pH may be further adjusted in mixingtank #2 615 by introducing sodium hydroxide (NaOH) 604 prior toseparation of barium sulfate 605. A flocculation aid (such as polymerand hydrochloric acid) from the polymer coagulant tank 625 may also beadded to the mixing tank #2 615 prior to separation of barium sulfate605.

The effluent from the first chemical precipitation stage may then beconcentrated 640 and subsequently crystallized 645 to obtain dry salt650 which may be further processed to make sodium hypochlorite 652 orliquid salt solution 651.

The liquid salt solution 651 collected from the crystallization step maythen be fed into another chemical precipitation step to obtain strontiumcarbonate (SrCO₃) and/or calcium carbonate (CaCO₃) 630.

This is done by introducing reagents, including but not limited to,sodium hydroxide (NaOH) 604, sodium carbonate (Na₂CO₃) 617, aflocculation aid from the polymer coagulant tank 625 may be added tomixing tank #3 620. The liquid salt solution 651 is then chemicallytreated in the mixing tank #3 620 and the pH may be adjusted to fromabout 11.5 to about 12.0 prior to separation of strontium carbonateand/or calcium carbonate 630.

The inventors have learned that if strontium is precipitated out beforethe crystallization step, a large amount of calcium is precipitatedalong with strontium during the chemical precipitation step, reducingthe overall amount of pure salt products. Accordingly, in a preferredembodiment, strontium carbonate is precipitated out after thecrystallization step from the pure salt solution.

In another preferred embodiment, prior to the chemical precipitationprocess, the flowback fracwater is tested to identify the primaryconstituents. Based on identification of the constituents, a series oftreatability studies can be performed to determine the effective amountof reagents to be added to remove the desired constituents from theflowback fracwater.

Providing a concentrated flowback brine 120 with the constant amount ofconstituents to be removed/contaminants is very important in overalleffectiveness of certain preferred embodiments of the chemicalprecipitation process. If there is significant variation in constituentconcentrations, specifically the two principal constituents, barium andstrontium, there is a potential need to re-treat previously treatedflowback brine to remove additional desired materials. This can wastetime, energy and money. If too much reagent is added, not only is a newsource of contamination introduced, but the process becomes inefficientand wasteful. Therefore, being able to monitor, sample and evaluate thechemical constituents of the brine and adjust the chemical precipitationsteps accordingly can improve the chemical precipitation processperformance and/or maximize pollutant removal efficiencies—an importantstep for ensuring the cost effectiveness. Thereafter, the appropriateamount of reagents can be added in accordance with the testing results.

After conducting a demonstration project at a site in Pennsylvania, theinventors learned that the concentrations and constituents of theflowback water vary significantly on a daily basis. Moreover, every wellwas producing a significantly different quality having differentconcentrations and constituents of the flowback water.

In addition, the inventors have learned that conducting a chemicalprecipitation process on-site may not be as cost effective since it mustbe designed to operate during the cold months of the year depending onthe location of the well. It was also difficult to monitor, sample andevaluate the chemical constituents of the brine and adjust the chemicalprecipitation steps accordingly due to the variability in theconcentrations and constituents of the flowback water. In short, theenergy and labor cost involved in running an effective chemicalprecipitation process on-site may therefore be high.

Accordingly, rather than chemically treating the flowback water on acontinuous or semi-continuous basis on-site, in a preferred embodiment,the present invention contemplates concentrating the flowback waterfirst on-site and returning the clean condensate produced by theevaporator to the drilling site for reuse, and trucking the concentratedflowback brine, which is now much lower in volume, to an off-site plantfor chemical precipitation and crystallization processes.

This provides advantage in the overall cost and efficiency of thechemical treatment process since the concentration and the constituentsto be precipitated out of the flowback brine in the concentrated brinecan be adjusted at to a constant level by mixing different batches ofthe flowback brine before introducing the water to the chemicalprecipitation process.

Crystallization

The chemically treated brine can be sent to one or more crystallizationstep 212B as shown in FIG. 2. The chemically treated concentrated brinemaybe also be stored in holding tanks 700 prior to and/or instead offurther processing.

The effluent brine can be crystallized using various methods known inthe art, including but not limited to, using multi-effect evaporators,one or more mechanical vapor recompression evaporators, or combinationsthereof. For example, FIG. 6 provides a simplified process flow diagramof the crystallization step using multi-effect evaporators. FIG. 7illustrates using a mechanical vapor recompression evaporator 801 forthe crystallizing step.

As illustrated in FIG. 6, in accordance with one embodiment of thepresent invention, the concentrated and chemically treated brine mayflow through a three-stage distilling process 720, 730, and 740 whichyields two products, i.e., steam 750 and a much more highly concentratedbrine 760. From steam generated 750, distilled water 790 may be producedwhich may be returned to the environment or may be reused ashydro-fracturing water. The sludge component 765 produced by this pointin the process has a total solid concentration well over 100,000 ppm. Tofurther concentrate the sludge, it is next run through thickeningprocess 770 that removes more of its liquid component. Finally, theconcentrated sludge 775 from the thickening process may be centrifuged780, producing two products 785: concentrated salt solution 785 and drysalt, in addition to the pure distilled water 790.

The liquid component from the centrifuging process is a high quality,over 98%, preferably over 99%, and more preferably 99.5% pureconcentrated salt solution that can be used for dust control since it isa solution of calcium, sodium and magnesium chlorides, and for roadwayde-icing. The ‘dry’ product of the centrifuging operation is over 98%,preferably over 99%, and more preferably 99.5% pure salt of a commercialgrade that has 0.1% moisture or less and can be bagged and sold forwater softening, pool water treatment, and other similar application.

In a preferred embodiment, over 98% pure dry salt, preferably over 99%pure dry salt, more preferably over 99.5% pure dry salt of sodiumchloride is further processed to produce sodium hypochlorite byconventional methods known in the art. Units manufactured by Siemenscalled CHLOROPAC or acceptable other equivalents could be chosen andutilized for this purpose.

Table 6 indicates the respective characteristics, volume and weights ofthe salt products generated by an initial 150,000 gpd frac-water input103 into the process.

TABLE 6 Influent Flow 56,160 gpd TDS 120,000 ppm TSS 0 ppm O&G 0 ppmEffluent- Flow 37,440 gpd Condensate TDS 10 ppm TSS 0 ppm O&G 0 ppmEffluent-Saturated Flow 18,720 gpd (Volume can vary TDS 36,000 ppm bymarket demand) TSS 0 ppm O&G 0 ppm Effluent-Dry Salt Moisture 0.1% (Masscan vary by Mass of Solids 50,585 lb/day market demand) Evaporator HeatSource Steam No. of Effects Three No. of Three Separation Centrifuge One

It should be noted that once the well-drilling operation is complete andmajor portion of the flowback fracwater has been collected and treated,the production of natural gas from a particular well will continue toproduce smaller amounts of fracwater combined with water fromunderground aquifers penetrated by the well (“production brine”). Suchproduction brine will continue to be collected for the life of the welland treated.

The production brine may be transported to the brine treatment plant asshown in FIG. 1, where it will go through preseparation,ultrafiltration, concentration, chemical precipitation andcrystallization steps to yield the same end-products as the process thatoccurs at the time of the drilling/hydro-fracturing operation 203.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method for making pure salt from hydro-fracturing wastewatercomprising: recapturing the hydro-fracturing wastewater selected fromthe group consisting of post-drilling flowback water and productionbrine water from hydro-fracturing, wherein the hydro-fracturingwastewater comprises benzene, ethylbenzene, toluene, xylene, barium,calcium, sodium and strontium; preheating the hydro-fracturingwastewater to produce a preheated hydro-fracturing wastewater; removingoil from the preheated hydro-fracturing wastewater; filtering thehydro-fracturing wastewater to remove solid particulates and largeorganic molecules to form a filtered and oil-removed hydro-fracturingwastewater, wherein the large organic molecules comprise the benzene,the ethyl benzene, the toluene, and the xylene; evaporating the filteredand oil-removed hydro-fracturing wastewater to produce a concentratedbrine containing from about 15 wt % to about 30 wt % of salt relative tototal weight of the concentrated brine and a first clean waterdistillate; recovering the first clean water distillate containing lessthan 500 ppm of total dissolved solids; using the first clean waterdistillate as source water for hydro-fracturing or returning the firstclean water distillate to environment; sampling the concentrated brineto determine an effective amount of at least one reagent to be added tothe concentrated brine to remove at least one desired chemicalconstituent from the concentrated brine, adding the effective amount ofthe at least one reagent to the concentrated brine to perform a chemicalprecipitation process to produce a chemically treated brine and at leastone precipitate comprising the at least one desired chemicalconstituent; separating the at least one precipitate comprising the atleast one desired chemical constituent from the chemically treatedbrine, wherein the desired chemical constituent is selected from thegroup consisting of barium and strontium; introducing the chemicallytreated brine to a crystallization step using a mechanical vaporrecompression evaporator, multi-effect evaporator or a combinationthereof to produce sodium chloride solid, calcium chloride solution anda second clean water distillate; recovering the sodium chloride solid;drying the sodium chloride solid to produce over about 98% pure drysodium chloride; recovering the calcium chloride solution, wherein thecalcium chloride solution is over about 98% pure; recovering the secondclean water distillate containing less than 500 ppm of total dissolvedsolids; and using the second clean water distillate as source water forhydro-fracturing or returning the second clean water distillate toenvironment.
 2. The method of claim 1, wherein the amount of salt in theconcentrated brine is from about 20 wt % to about 30 wt % relative tothe total weight of the concentrated brine.
 3. The method of claim 1,further comprising a step of converting the dry sodium chloride tosodium hypochlorite.
 4. The method of claim 1, wherein said dry sodiumchloride and said calcium chloride solution are over 99% pure.
 5. Themethod of claim 4, wherein said dry sodium chloride and said calciumchloride solution are over 99.5% pure.
 6. The method of claim 1, whereinthe steps of preheating the hydro-fracturing wastewater, removing oilfrom the hydro-fracturing wastewater, filtering the hydro-fracturingwastewater-, and evaporating to produce the concentrated brine areperformed on-site where the hydro-fracturing waste water is produced. 7.The method of claim 1, wherein the steps of adding the effective amountof the at least one reagent to perform the chemical precipitationprocess, separating the at least one precipitate, introducing thechemically treated brine to the crystallization step, recovering thesodium chloride solid, and recovering the calcium chloride solution areperformed at an off-site plant.
 8. The method of claim 1, wherein thereagent is a compound selected from the group consisting of sodiumsulphate, potassium permanganate, aluminum chloride, sodium carbonate,sodium hydroxide, hydrochloric acid and mixtures thereof.
 9. The methodof claim 8, wherein the compound is sodium sulphate.
 10. A method formaking pure salt from hydro-fracturing wastewater comprising:recapturing the hydro-fracturing wastewater selected from the groupconsisting of post-drilling flowback water and production brine waterfrom hydro-fracturing, wherein the hydro-fracturing wastewater comprisesbenzene, ethylbenzene, toluene, xylene, barium, calcium, sodium andstrontium; preheating the hydro-fracturing wastewater to produce apreheated hydro-fracturing wastewater; removing oil from the preheatedhydro-fracturing wastewater; filtering the hydro-fracturing wastewaterto remove solid particulates and large organic molecules to form afiltered and oil-removed hydro-fracturing wastewater, wherein the largeorganic molecules comprise the benzene, the ethylbenzene, the toluene,and the xylene; sampling the filtered and oil-removed hydro-fracturingwastewater to determine an effective amount of at least one reagent tobe added to the concentrated brine to remove at least one desiredchemical constituent from the filtered and oil-removed hydro-fracturingwastewater, adding the effective amount of the at least one reagent tothe filtered and oil-removed hydro-fracturing wastewater to perform achemical precipitation process to produce a chemically treated brine andat least one precipitate comprising the at least one desired chemicalconstituent; separating the at least one precipitate comprising the atleast one desired chemical constituent from the chemically treatedbrine, wherein the desired chemical constituent is selected from thegroup consisting of barium and strontium; introducing the chemicallytreated brine to a crystallization step using a mechanical vaporrecompression evaporator, multi-effect evaporator or a combinationthereof to produce sodium chloride solid, calcium chloride solution anda clean water distillate; recovering the sodium chloride solid; dryingthe sodium chloride solid to produce over about 98% pure dry sodiumchloride; recovering the calcium chloride solution, wherein the calciumchloride solution is over about 98% pure; recovering the clean waterdistillate containing less than 500 ppm of total dissolved solids; andusing the clean water distillate as source water for hydro-fracturing orreturning the second clean water distillate to environment.
 11. Themethod of claim 10, wherein said dry sodium chloride and said calciumchloride solution are over 99% pure.
 12. The method of claim 11, whereinsaid dry sodium chloride and said calcium chloride solution are over99.5% pure.